Provided are a magnetic disk and a method of fabricating the magnetic disk. The magnetic disk includes an aluminum alloy plate fabricated by a process involving a CC method and a compound removal process, and an electroless NiP plating layer disposed on the surface of the plate. The aluminum alloy plate is composed of an aluminum alloy containing 0.4 to 3.0 mass % (hereinafter abbreviated simply as %) of Fe, 0.1% to 3.0% of Mn, 0.005% to 1.000% of Cu, 0.005% to 1.000% of Zn, with a balance of Al and unavoidable impurities. In the magnetic disk, the maximum amplitude of waviness in a wavelength range of 0.4 to 5.0 mm is 5 nm or less, and the maximum amplitude of waviness in a wavelength range of 0.08 to 0.45 mm is 1.5 nm or less.

Provided are: an aluminum alloy substrate for a magnetic disk, including an aluminum alloy including 0.4 to 3.0 mass % of Fe with the balance of Al and unavoidable impurities; a method for producing the aluminum alloy substrate for a magnetic disk; and a magnetic disk in which an electroless NiP plating treatment layer and a magnetic layer formed thereon are disposed on a surface of the aluminum alloy substrate for a magnetic disk.

There are provided: an aluminum alloy magnetic disk substrate including: an aluminum alloy base material including an aluminum alloy containing 0.4 to 3.0 mass % (hereinafter, simply referred to as %) of Fe, 0.1 to 3.0% of Mn, 0.005 to 1.000% of Cu, and 0.005 to 1.000% of Zn, with the balance of Al and unavoidable impurities; and an electroless NiP plated layer formed on a surface of the aluminum alloy base material, in which the peak value (BLEI) of Fe emission intensity at an interface between the electroless NiP plated layer and the aluminum alloy base material, as determined by a glow discharge optical emission spectrometry device, is lower than Fe emission intensity (AlEI) in the interior of the aluminum alloy base material, as determined by the glow discharge optical emission spectrometry device; and a method for producing the aluminum alloy magnetic disk substrate.

A base for a magnetic recording medium, includes a substrate made of an Al alloy and having a surface, and a film made of a NiWP-based alloy and plated on the surface of the substrate. The film includes W in a range of 15 mass % to 22 mass %, P in a range of 3 mass % to 10 mass %, and Pb in a range of 0.03 mass % to 0.08 mass %. The film has a thickness of 5 m or greater.

A magnetic disk substrate having a flat main surface, an end face, and a chamfered face formed between the main surface and the end face. The substrate has an offset portion, present on the main surface within a range of 92.0 to 97.0% in a radial direction from a center of the substrate. A distance from the center of the substrate to the end face of the substrate in a radial direction is 100%, the offset portion being raised or lowered with respect to a virtual straight line connecting two points on the main surface, set at positions of 92.0% and 97.0%. A maximum distance from the virtual straight line to the offset portion in a direction perpendicular to the virtual straight line is a maximum offset value.

A magnetic recording medium substrate is provided in which a NiP type plating film is formed on a surface of an aluminum alloy substrate that includes Si in a range of 9.5 mass % or more and 11.0 mass % or less, Mn in a rage of 0.45 mass % or more and 0.90 mass % or less, Zn in a range of 0.32 mass % or more and 0.38 mass % or less, Sr in a range of 0.01 mass % or more and 0.05 mass % or less. In the alloy structure of the aluminum alloy substrate, an average particle diameter of Si particles is 2 m or less, the film thickness of the NiP type plating film is 7 m or more. An outer diameter of the magnetic recording medium substrate is 53 mm or more, the thickness is 0.9 mm or less, and the Young's modulus is 79 GPa or more.

A base for a magnetic recording medium, includes a substrate made of an Al alloy and having a surface, and a film made of a NiP-based alloy and plated on the surface of the substrate. The film has a thickness of 7 m or greater, and a ratio E/ is 29 or greater, where E [GPa] denotes the Young's modulus of the substrate, and [g/cm.sup.3] denotes a density of the substrate.

There are provided: an aluminum alloy magnetic disk substrate including: an aluminum alloy base material including an aluminum alloy containing 0.4 to 3.0 mass % (hereinafter, simply referred to as %) of Fe, 0.1 to 3.0% of Mn, 0.005 to 1.000% of Cu, and 0.005 to 1.000% of Zn, with the balance of Al and unavoidable impurities; and an electroless NiP plated layer formed on a surface of the aluminum alloy base material, in which the peak value (BLEI) of Fe emission intensity at an interface between the electroless NiP plated layer and the aluminum alloy base material, as determined by a glow discharge optical emission spectrometry device, is lower than Fe emission intensity (AlEI) in the interior of the aluminum alloy base material, as determined by the glow discharge optical emission spectrometry device; and a method for producing the aluminum alloy magnetic disk substrate.

Provided are a thin hard disk substrate that is scratch-resistant on the disk surface and wobbles less during rotation and a hard disk device including such a hard disk substrate. The hard disk substrate 1 includes an aluminum alloy substrate 2 having NiP plating films 3 on the surfaces. The aluminum alloy substrate 2 has the Vickers hardness of 60 Hv or more, the ratio between the thickness of the NiP plating films 3 and the thickness of the Al alloy substrate 2 is 3.8% or more, the Young's modulus of the hard disk substrate 1 is 74.6 GPa or more, and the Vickers hardness of the hard disk substrate 1 is 293 Hv or more.

A magnetic-disk substrate has a pair of main surfaces, and an arithmetic average roughness Ra of each of the main surfaces is 0.11 nm or less. The arithmetic average roughness Ra is a value obtained through measurement using an atomic force microscope provided with a probe having a probe tip provided with a carbon nanofiber rod-shaped member. The magnetic-disk substrate is made of glass or aluminum alloy.